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| Titel |
Detailed dayside auroral morphology as a function of local time for southeast IMF orientation: implications for solar wind-magnetosphere coupling |
| VerfasserIn |
P. E. Sandholt, C. J. Farrugia, W. F. Denig |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 22, no. 10 ; Nr. 22, no. 10 (2004-11-03), S.3537-3560 |
| Datensatznummer |
250015030
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| Publikation (Nr.) |
 copernicus.org/angeo-22-3537-2004.pdf |
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| Zusammenfassung |
| In two case studies we elaborate
on spatial and temporal structures of the dayside
aurora within 08:00-16:00 magnetic local time
(MLT) and discuss the relationship of this structure to
solar wind-magnetosphere interconnection topology
and the different stages of evolution of open field lines in the Dungey
convection cycle. The detailed 2-D
auroral morphology is obtained from continuous ground observations
at Ny Ålesund
(76° magnetic latitude (MLAT)), Svalbard during two days when the
interplanetary magnetic field (IMF) is directed southeast
(By>0; Bz<0). The auroral activity
consists of the successive activations of the following forms:
(i) latitudinally separated,
sunward moving, arcs/bands of dayside boundary plasma sheet (BPS) origin,
in the prenoon (08:00-11:00 MLT) and postnoon (12:00-16:00 MLT)
sectors, within 70-75° MLAT,
(ii) poleward moving auroral forms (PMAFs) emanating from
the pre- and postnoon brightening events,
and (iii) a specific activity appearing in the
07:00-10:00 MLT/75-80° MLAT
during the prevailing IMF By>0
conditions.
The pre- and postnoon activations are separated by
a region of strongly attenuated auroral activity/intensity within
the 11:00-12:00 MLT sector, often referred to as the midday gap aurora.
The latter aurora is attributed to
the presence of component reconnection at the
subsolar magnetopause where the stagnant magnetosheath
flow lead to field-aligned
currents (FACs) which are of only moderate intensity.
The much more active and intense aurorae in the prenoon (07:00-11:00 MLT)
and postnoon (12:00-16:00 MLT)
sectors originate in
magnetopause reconnection events that are
initiated well away from the subsolar point.
The high-latitude auroral activity in the prenoon sector (feature iii)
is found to be accompanied by a convection channel at the polar cap
boundary. The associated ground magnetic deflection (DPY)
is a Svalgaard-Mansurov effect.
The convection channel is attributed to effective
momentum transfer from the
solar wind-magnetosphere dynamo in the high-latitude
boundary layer (HBL), on the downstream side of the cusp. |
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